Update CHANGELOG.md

Author: chuongmep

CHANGELOG.md

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 # Changelog
 - 2022-12-16 **2.0.0**
   - Add support IronPython 3.4 [#136](https://github.com/architecture-building-systems/revitpythonshell/pull/136)
+  - Please follow [Upgrade from IronPython2 to IronPython](https://github.com/IronLanguages/ironpython3/blob/master/Documentation/upgrading-from-ipy2.md) to upgrade your code.
 - 2022-09-22 **1.0.2**
   - Fix set CollectorExt.m_app error. [#128](https://github.com/architecture-building-systems/revitpythonshell/pull/128)
 - 2022-06-27 **1.0.1**